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Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
I recently purchased a relatively inexpensive 400 amp AC digital clamp meter and it is not listed as True RMS. I do have another True RMS meter but I needed a clamp meter for high currents and for the convenience of not having to break the loop, etc. I plan to use this meter for common mains voltage readings for motors, heating elements, and also with devices using a homemade inductive ballast.
My question is if the measurements using the non "True RMS" meter will be inaccurate when used with inductive loads? I was under the impression that True RMS is really only used with non-sinusoidal waveforms, and wouldn't be affected with leading/lagging current or voltage, but now I'm not so sure.
Also, if I'm going to return this meter, can anyone recommend a respectable clamp multimeter? And how useful is it to most people to have the ability to measure both high current AC AND DC?
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
Things with a rectifier and a smoothing capacitor directly on the mains input (like older SMPSes and the like) draw a non-sinusoidal load current, and will most likely give wrong readings with a non-TRMS-meter.
Registered Member #396
Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176
Alright, thanks guys! Now how useful is a high current DC measurement? Anything with SSTC's? The only thing I can think of would pertain to car batteries or other large battery banks.
Hmmm . . . to take it back or to not take it back . . .
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True RMS Meters
